Antenna arrays can provide improved antenna performance by allowing control of phase and amplitude of the signals associated with various antenna elements in an antenna array. By adjusting signal phase or signal amplitude of separate antenna elements, information redundancy in various signals associated with various antenna elements can be used to form a desired beam signal. In particular, an antenna array can be steered by using variable phase shifters coupled to respective antenna elements in the antenna array to direct the antenna at a pointing angle. The phase shifters can be variable phase shifters configured to induce phase shifts for signals associated with various antenna elements in response to a set of commands. Setting relative phase between signals associated with various antenna elements allows the antenna to be directed or adjusted to appropriate pointing angles without physically moving the antenna elements.
There is a mathematical mapping between the radiating element amplitude and phase excitations of an active electronically scanned array (AESA) and the far field radiation pattern through a Fourier transform relationship. Aperture amplitude and phase errors therefore directly corrupt far field radiation performance. The goal of the AESA calibration is to minimize these errors, and ideally drive them to zero.
The prior art accomplishes calibrations various levels within the AESA subassembly: a) the Radio Frequency Integrated Circuits (RFIC) Transmit/Receive Module (TRM), the AESA feed manifold layer, just short of the radiative aperture layer, and c) within the radiated near field. Radiative near field calibration is the most powerful as it takes into account all mechanisms that contribute to radiation amplitude and phase errors, however, the prior art accomplish this only by means of expensive near field antenna measurement techniques.
Due to the complexity and test equipment expense, near field radiative measurements are accomplished only within a lab or a manufacturing line environment. This results in only a one-time “static” AESA calibration.
The “static” calibration dos not account for operational parameters of a field AESA system such as in-situ vehicular platform induced AESA performance distortion, ongoing prognostic/diagnostic monitoring of electronic device aging and catastrophic failures, or environmentally induced stresses. Furthermore, another deficit of the prior art in non-platform calibration is the inability to perform “self-healing” where the ensemble AESA TRMs are real-time monitored and adjusted for TRM performance degradation and/or catastrophic failure to maintain a prescribed overall AESA performance level. System “self-healing” can maximize system mean time between failures (MTBF), dispatchability and availability.